I think these topic's has been covered before but I can't find anything in the search engine..

Been asked to install a shower, low volatge extractor and move a light. I know the shower must be RCD protected, going to install a small CU for this, but should in this instance does the light and extractor also have to be on a RCD protected circuit. (Just started my 17th edition and looking at the On Site Guide this appears to be the case??)

Also if there is no bonding to the gas or water where do I stand on thi?Is this a 'must' before I start in bathroom?

No need to RCD the feed to the power supply for the LV fan, if that supply unit is in the roof space and thus outside the bathroom.

Have to disagre with you there.

The requirement is for the circuits of the location to be RCD protected.

there is no exception made because an appliance is ELV.

According to the ESC there will be an exception regarding ELV in a future update - but I have to agree with spin that at present the circuit feeding the fan should be RCD protected. Probably a moot point anyway as it is likely to be switched with the light and as that is being moved will need RCD protection anyway.